Two-Phase Particle Image
Velocimetry (PIV)
Supported by the National Science Foundation under Grants #CTS-9702723 & CTS-9871156
One of the most challenging problems in the area of dilute two-phase flows is trying to predict and understand the interaction of particles with a turbulent carrier fluid. Although much work has been done in this area through the use of numerical simulation, there are many unanswered questions that require experimental observation.
Along these lines, instrumentation needs to be developed which will allow detailed measurements of the spatially resolved, instantaneous velocity field of both phases, as well as the concentration of the dispersed phase. Previous work has been done which provides a statistical single-point description, and conditional averaging of coherent structures has allowed for a view into the structure of well-organized flows, but a method for examining the interaction a the smaller scales of the flow remains is still in its infancy.
Research at our two-phase laboratory is currently working on extending single-phase Particle Image Velocimetry techniques to measure quantities important to understanding dilute two-phase coupling within turbulent flows. These techniques utilize high-speed imaging, scanning light sheets and advanced image processing for discrimination and quantification of the separate phases. The current method we have developed uses image pairs from a single camera and a median filter to separate the information of the two phases (See figure 1). Once the images have been separated, standard cross-correlation PIV methods are used to extract the carrier phase motion, and particle tracking methods are used to determine the location and displacements of the dispersed phase. The information is then recombined to provide a simultaneous, spatially resolved description of the coupled particle/fluid motion. 
Click diagram for
larger image
This method works well in two-phase flows where there is a distinct size difference within the image between the dispersed phase and the tracers particles used to track the carrier fluid motion. Details on the method and its validation can be found in the article:
1. Kiger, K. T. & Pan, C., PIV technique for simultaneous measurement of dilute two-phase flows, Journal of Fluids Engineering, 122(4), pp 811-818, 2000.
Related conference proceedings and presentations:
1. K. Kiger & C. Pan, Two-Phase PIV for Dilute Solid/Liquid Flow, 3rd International Workshop on Particle Image Velocimetry, Santa Barbara, CA, September 16-18, 1999.
2. K. Kiger & C. Pan, Simultaneous Two-phase PIV of Dilute Liquid/Solid Flows, Proceedings of the First International Symposium on Turbulence and Shear Flow Phenomena, Santa Barbara, CA, September 12-15, 1999.
3. K. T. Kiger, Scanning PIV technique to resolve dispersed two-phase flow, Third International Conference on Multiphase Flow - ICMF98, Lyon, France, June 8th-12th, 1998.
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